It has an RGB notification LED which I've always be quite fond of when I've seen a similar thing on the blackberry phones.

It also features wolfson DAC audio. Now I don't pretend to know everything about audio, but from the gist of things I am led to believe that it is a good thing.

Intrestingly enough HTC used an RGB noticication LED on the Desire, not sure about the Nexus, and not sure about other HTC phones, HTC just used it for the standard green and orange, but apps like go messenger I think it was can use other colours.

Nexus is out the window with no sd expansion is a no buy on top of not upgrade path to ICS and not a big fan of "3D" phones so it leaves the sensation or S2 then I guess.

No you're stuck with 16GB on the Nexus S but it does have ICS, it was one of the first to get it as an OTA update (well, if you ignore that they rolled it out, then stopped and then rolled it out again).